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polyethene

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addition polymer

plastic bottles, toys, plastic bags, film wrap

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polychloroethene/PVC

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addition polymer

plastic pipes, artificial leather, wire insulation

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21 Terms

1
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polyethene

addition polymer

plastic bottles, toys, plastic bags, film wrap

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polychloroethene/PVC

addition polymer

plastic pipes, artificial leather, wire insulation

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PTFE

addition polymer

coating for non-stick pans

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polypropene

addition polymer

lab equipment, automobile parts

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polystyrene

addition polymer

styrofoam

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starch/glucose

  • enzymes act as biological catalysts

  • condensation polymerisation of glucose (monomer) into starch (polyamide) + water

  • reverse: hydrolysis, break down polymer into monomers using water

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polyethylene terephthalate (PET)

low permeability to CO2, used in bottling of canned drinks

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kevlar

polyamide with benzene ring

spider silk (naturally occuring)

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polypeptide

polyamide formed from amino acids

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renewable energy sources

naturally replenished, will not run out

  • biofuels

  • solar energy

  • wind

  • hydroelectric

  • tidal

  • geothermal

  • nuclear fusion

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non-renewable energy sources

finite, will run out

  • fossil fuels (coal oil natural gas)

  • nuclear fission

  • electrochemical cells: redox reaction generates electricity

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formation of fossil fuels

  • plant matter contains CHO from photosynthesis (glucose) + contains N and S because of protein. plants consumed by animals.

  • anaerobic decay of biological material: absence of oxygen, compressed and acted on by bacteria

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coal

  • formed from remains of plants that were buried → partial decomposition in absence of oxygen, high temperature and pressure

  • mostly carbon, also HONS

  • % of C increases, burn more cleanly and releases more heat on combustion

advantages

  • supply should last 100s of years

  • distributed throughout the world

  • can be converted to synthetic gaseous/liquid fuels

  • can be converted to feedstock for the petrochemical industry

  • more concentrated source of energy

  • relatively cheap to produce

disadvantages

  • produces greenhouse gases when burned → climate change

  • acid rain + particulates

  • less easy to transport

  • mining is dirty and dangerous

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crude oil (petroleum)

  • formed from remains of plankton that sank to bottom of sea and buried → absence of oxygen, high pressure, moderate heat (60-170C)

  • is a mixture of hydrocarbons, also ONS

advantages

  • easier to extract and transport than coal

  • convenient for internal combustion engine

  • source of variety of chemicals for the petrochemical industry

disadvantages

  • produces greenhouse gases when burned → climate change

  • acid rain

  • supply could run out in decades

  • extraction + transportation in tankers → env issues

  • few countries have reserves

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natural gas

  • formed from remains of plankton that sank to bottom of sea and buried → absence of oxygen, high pressure, moderate heat (60-170C)

  • mostly CH4 and light hydrocarbons and HS

advantages

  • cleanest fossil fuel due to low % of C

  • easiest to extract and transport (using pipes)

  • releases highest amount of energy per mass of fuel

  • produces least CO2 per J of energy

  • cheap to produce: is a byproduct of coal/oil production

disadvantages

  • produces greenhouse gases when burned → climate change

  • acid rain

  • supply could last less than 100 years

  • few countries have reserves

  • risk of explosions due to leaks

  • most difficult to store because it is a gas: need store under pressure or cool to liquefy it

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ways of comparing fossil fuels

  1. CO2 produced per J

    • vol or mol of CO2 / energy divided by 1000 = __ mol CO2 J -1

    • lowest = greenest (natural gas)

  2. vol of fuel per mass of fuel

    • no. of mol x 22.7 divided by mass = __dm3g-1

    • only if at STP

  3. mass of CO2 produced per gram of fuel burned

    • mol x 44.01 = mass of CO2

      mass of CO2/Mr of fuel = __g

  4. carbon footprint

    • mass of fuel consumed = density x volume

    • no. of mol of fuel consumed = mass/Mr

    • mol ratio to find no. of mol of CO2 produced

    • mass of CO2 = no. of mol x 44.01 = __g

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how could samples be distinguished by combustion?

calculate % of C for each sample. sample with higher % of C has higher tendency for incomplete combustion, will produce more soot when burnt.

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greenhouse effect

  • initial: some IR reflected back into space, some reach earth’s surface, some absorbed by greenhouse gases then re-radiated back to earth

  • earth’s surface emits IR radiation, absorbed by molecules of greenhouse gases (CO2, CH4, NOx) → promote to higher energy levels, vibrate more → as move down to ground state, energy given out in all directions → some IR radiation radiated back to earth

    • recall IR spec: only for asymmetric stretch and symmetric bend since there is change in dipole moment

    • carbon dioxide has greater influence on global warming: even though doesn’t absorb much IR radiation, produced in greater amounts

  • net effect: higher % of solar energy is trapped in atmosphere → higher average global temperatures

  • impact: crop yields decrease, biodistribution (due to desertification and loss of cold-water habitats), rising sea levels (due to melting of ice caps)

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biofuels

  • plants have CHO because of photosynthesis producing glucose → plant material transformed into fuel

advantages

  • renewable source of energy

  • can be produced locally, no need expensive oil imports

  • can be produced from waste materials

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ethanol as biofuel

formed from fermentation of glucose

  • C6H12O6 (aq) → 2C5H5OH (aq) + 2CO2 (g)

  • conditions: ethanol, yeast catalyst, 37C, absence of oxygen (prevent oxidation of ethanol)

  • produces mixture of water, aldehydes, other alcohols and around 8% ethanol, need distillation to concentrate % of ethanol

    • methanol poisoning

    • max concentration 15% ethanol since higher concentration will poison the yeast

  • exothermic reaction, need control temperature otherwise will denature enzymes and kill yeast

advantages

  • lower greenhouse emissions: produces CO2 but the C in ethanol came from atmosphere (absorbed by plants), so theoretically ‘carbon neutral’

  • renewable, produced locally

disadvantages

  • lower specific energy than gasoline, need larger volume for same amount of energy

  • absorbs moisture from atm, damages engine

  • production of ethanol is energy intensive (distillation)

  • food vs fuel, price of food increases

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biodiesel

formed from transesterification of vegetable oils

  • 3 fatty acids (carboxylic acid) + glycerol (triol) → vegetable oils (triglyceride, 3 ester linkages)

  • methanol react with vegetable oil → fatty acid ester link to methanol

  • condition: strong base catalyst

  • reversible reaction, so excess methanol added to shift POE to right

advantages

  • biodegradable, less env impact from spillage

  • no S, no SO2

  • better lubricant than petrodiesel (reduce engine wear)

  • theoretically carbon neutral

disadvantages

  • higher NOx emissions

  • more expensive than petrodiesel

  • lower specific energy than petrodiesel, need larger volume for same amount of energy

  • production is energy intensive

  • food vs fuel, price of food increases

  • loss of biodiversity for palm oil plantations